Images from NASA's Chandra X-ray Observatory reveal
previously unobserved features in the remnants of three
different supernova explosions. Two of the remnants,
G21.5-0.9 and PSR 0540-69, show dramatic new details of
the prodigious production of energetic particles by a
rapidly rotating, highly magnetized neutron star, as
well as the enormous shell structures produced by the
explosions. The striking image of the supernova remnant
E0102-72 shows puzzling spoke-like structures in its
interior.

E0102-72 is a supernova remnant in the Small Magellanic Cloud,
a satellite galaxy of the Milky Way. This galaxy is 190,000
light years from Earth. E0102 -72, which is approximately a
thousand years old, is believed to have resulted from the
explosion of a massive star. Stretching across forty light years
of space, the multi-million degree source resembles a flaming
cosmic wheel.

The identification of G21.5-0.9 as the remnant of a supernova
explosion is based on indirect evidence from radio and X-ray
observations. At both radio and X-ray wavelengths, it appears as
round patch in the sky. Detailed observations with radio
telescopes confirm that the radio waves are produced by high
energy electrons spiraling around magnetic field lines
(synchrotron radiation). The X-rays are probably produced by the
same process, but the electrons involved have energies many
thousands times higher than those that produce the radio waves.
The favored theory is that the high-energy electrons responsible
for both the radio and X-ray emission are produced by a rapidly
rotating, highly magnetized neutron star left behind when a
massive star exploded some 40,000 years ago.

PSR 0540-69 is a neutron star, or pulsar, that is rotating very
rapidly, making a complete rotation every one-twentieth of a
second. It is similar in many ways to the famous Crab Nebula
pulsar. Both objects are spinning rapidly, are about 1,000 years
old and are surrounded by a large cloud of gas and high-energy
particles. The surrounding cloud in both cases is powered by the
conversion of rotational energy of the neutron star into high
energy particles through the combined action of rapid rotation
and a strong magnetic field. PSR 0540-69 is 160,000 light years
away in the Large Magellanic Cloud, one the Milky Way's small
satellite galaxies.